1. Field of the Invention
The invention relates to a method for fabricating an image sensor, and more particularly, to a method of using the patterned photomask of forming microlenses for fabricating color filters.
2. Description of the Prior Art
As the development of electronic products progresses, the demand for related components has increased as well. For example, as the development of digital cameras and scanners progresses, the demand for image sensor increases accordingly. In general, today's image sensors in common usage are divided into two main categories: charge coupled device (CCD) sensors and CMO image sensors (CIS). The application of CMOS image sensors has increased significantly for several reasons. Primarily, CMOS image sensors have certain advantages of offering low operating voltage, low power consumption, and the ability for random access. Additionally, CMOS image sensors are currently capable of integration with the semiconductor fabrication process.
The CMOS image sensor separates (i.e., classifies) incident light into a combination of light of different wavelengths. The light of different wavelengths is received by respective sensing elements and is subsequently transferred into digital signals of different intensities. For example, the CMOS image sensor can consider incident light as a combination of red, blue, and green light. Those wavelengths are subsequently received by photodiodes, and then transformed into digital signals. However, in order to separate incident light, a monochromatic color filter array (CFA) must be set above every optical sensor element.
Nevertheless, conventional method for fabricating a color filter array typically involves the step of forming the color filters directly on the surface of a passivation layer, and covering a planarizing layer and forming a plurality of microlenses corresponding to the color filters thereafter. As the color filters are formed on the passivation layer, this design not only increases the path of light traveling to the photodiodes in the substrate, but also results in peeling of color filters and affects the performance of the image sensor.